Method of electroplating copper elbows



1962 M. A. DIKE 3,051,632

METHOD OF ELECTROPLATING COPPER ELBOWS Filed July 27, 1959 INVENTOR.lZszr/zzf Xena ye .D/KE

ATTORNEYS iQEEE 3,5l.,fi32 Patented Aug. 28, 1962' This inventionrelates generally to electroplating and more particularly to anelectroplating process for rebuilding the stretched area of mechanicallybent tubes to a minimum thickness.

In forming a pipe fitting, such as an elbow, a length of thin-walledinitially straight copper tubing is bent into curved form by standardmechanical bending processes. Under such conditions, it is impossible tomaintain uniformity of tube wall thickness because the metal of theouter wall or convex surface of the tubing is stretched and thus thinnedto an unsafe or unsatisfactory extent. This thinning results in agradual reduction of the convex wall thickness that gradually thinsdownwardly from a plane substantially coinciding with the lower edge ofthe inner concave surface.

It is a main object of this invention to provide an electroplatingprocess for rebuilding such thinned curved surface to a desired minimumthickness.

Another object of this invention is to provide an electroplating methodfor rebuilding the stretched surfaces of mechanically bent elbows sothat such elbows may be formed of straight tubes of minimum originalthickness.

Still another object of this invention resides in the manner ofcontrolling the immersion of the copper elbows in the electrolyte sothat uniformity of the re-built Wall surface is maintained.

A further object of this invention is to provide a controlledelectroplating process particularly designed to rebuild and reinforcereduced or stretched metal areas to at least minimum original tube wallthickness.

A still further object of the invention is to provide a controlledwithdrawal of the stretched copper elbows from the electrolyte so thatthe deposit or plating material will be gradually increased to regain atleast minimum original straight tube thickness.

A further object is to form an elbow from a metal tube having a minimumwall thickness by first bending said tube into the shape of said elbowand then electroplating the portion of said tube that is thinned by suchbending so as to rebuild said portion to said minimum wall thickv ness.

An additional object of the present invention is to provide an elbowmechanically bent from a tube of minimum wall thickness wherein theportion of said tube that is thinned by such bending is covered by alayer of electroplated material whereby said elbow will have a minimumwall thickness throughout its length.

With the foregoing objects in view, and such other objects andadvantages as will become apparent to those skilled in the art to whichthis invention relates as this specification proceeds, the inventionconsists essentially in the arrangement and construction of parts all ashereinafter more particularly described, reference being had to theaccompanying drawing in which:

FIGURE 1 is a perspective view of a thin-walled copper tube before it ismechanically bent into the shape of an elbow;

FIGURE 2 is a perspective view of the tube of FIG- URE 1 after it hasbeen bent into an elbow shape;

FIGURE 3 is a vertical sectional view taken on the line 3-3;

FIGURE 4 is a sectional View similar to FIGURE 3 showing the same elbowfollowing the rebuilding process of the present invention;

FIGURE 5 is a side elevational 'view taken partly in vertical sectionand showing an elbow-plating mechanism useful in carrying out theprocess of the present invention;

FIGURE 6 is a sectional view taken on the line 66 of FIGURE 3; and

.FIGURE 7 is a sectional view taken on the line 7-7 of FIGURE 4.

Referring to the drawing, a thin-walled straight copper It is standardpractice that the tube tube is shown at 10. 10 be mechanically bent toform an elbow E. Any conventional mechanical bending process may be usedto bend the elbow E to any desired degree of curvature.

Irrespective of the degree of elbow curvature, the mechanical bendingoperation will always stretch and thin the metal of the outer wall orconvex surface 11, as shown in FIGURES 3 and 6. The stretching of theelbow outer wall surface results in a gradual reduction or feathering ofmetal from substantially the beginning of the convex area at 12 to theextreme outer point indicated at 11, as shown in FIGURE 3. Thisreduction of wall thickness results in a corresponding reduction ofstrength and useful service life.

Previously it has been necessary to process elbows from straight tubingof considerable thickness and weight in order to provide a sufficientlysafe and durable stretched convex surface area. The added material costdid not change the fact that the processed elbows were only as strong astheir stretched and thinned outer walls. It is highly desirable that theconsiderable expense of the above process be materially reduced.

The present invention permits the use of straight tubing of minimum wallthickness and provides an entirely satisfactory copper electroplatingprocess for rebuilding the stretched and thinned outer elbow surface tosubstantially uniform tube wall thickness. Referring now to FIGURE 5,this process utilizes a standard electroplating tank 16 containing thedesired copper plating electrolyte B. It is preferable that theelectrolyte B be composed of an acid copper solution or a cyanide coppersolution; however, other conventional electroplating solutions may alsobe. utilized. A conventional copper anode preferably of electrolyticcopper is shown at A disposed in the tank 16. Plural copper elbows E arereleasably secured to an immersion bar 18 as by conventional clips 19.The bar 18 has a standard electrical connection 20 and complete theelectroplating circuit with the elbows E forming the cathode C. Theimmersion bar 18 is threaded at 21 and 21 on duel feed screws 22 and 23,respectively. The feed screws 22 and 23 are supported at their lowerends in dual brackets 24 and 25, respectively, and dual frames 26 and 27rising from said brackets support the upper ends of the feed screws 22and 23. The frames 26 and 27 also provide bearing support for ahorizontally disposed feed screw drive shaft 28. The drive shaft 28carries beveled gears 29 and 30 that mesh with similar beveled gears 31and 32 on the upper end of the feed screws 22 and 23, respectively.

Means for actuating the drive shaft 28 and feed screws 22 and 23 toraise and lower the immersion bar 18 is provided in a standard variablespeed reversible electric motor M drivingly connected to a conventionalspeed changing mechanism T having a driven shaft 34 coupled with thedrive shaft 28. This speed changing mechanism T includes a control wheel36 which is manipulated so as to vary the ratio of the speed of theshaft of electric motor M relative to the speed of the driven shaft 34and hence shaft 28. The exact details of construction of the electricmotor M and the speed changing mechanism T are not important to thescope of the present invention.

Moreover, other means; accomplishing the same results may be usedwithout departing from the scope of. the.

present invention. a a H In conducting the present process,after'mechanical bending of the copperelbows has been accomplished, theelbows E are clipped to the bar 18 and lowered into the electrolyte B sothat preferably only the stretched sur- .fac'e areas to be rebuilt areimmersed. An electric circuit is then completed between the anode andthe cathode through the electrolyte; Inorder that the plating of thethinned tubular wall surface is uniform, the speed changing mechanism Tis set to slowly withdraw the elbows E from the electrolyte B during theplating operation so that the plating material will be deposited inincreasing thickness from the point 12 to the point 11 of 7 FIGURE 3.The gradual depositing of the plating material rebuilds and reinforcesthe initially bent elbow of FIGURES 3 and 6 to the thicknessof thecompleted elbow of FIGURES ,4 and 7. Control of the electric currentduring the aforedescribed electroplating process may follow conventionalelectroplating practice.

Since variou modifications can be made in the invention as hereinabove'described, and many apparently widely difiierent embodiments of samemade within the spirit and scope of the claims without departing fromsuch spirit and scope, it is intended that all matter con-' tained inthe accompanying specification shall be interpreted as illustrative onlyand not in a limiting sense.

I claim:

1. A method of forming an elbow having uniform wall thickness out ofcopper tubing comprising the steps of,

bending the copper tubing into theshape of an elbow, locating the wallportions of said elbow which meet reduced thickness due to such bending,and electroplating onto said wall portions suflicient copper to overcomesaid reduced thickness to thereby provide an elbow of uniform wallthickness. V I

2. A method of forming an elbow having uniform wall thickness out ofcopper tubing comprising the steps of,

bending the copper tubing into the shape of an elbow,

locating the wall portions of said elbow which are 'ofreduced'thicknessdue to such bending, immersing said wall age-51532 duced thickness dueto such bending, immersing said Wall portions in an electrolyticsolution, activating said solu- 1 tion to effect electroplating, andwithdrawing said wall portion -from said electrolytic solution at apredetermined rate to provide an elbow of uniform thickness.

4. A method of forming an elbow having uniform wall thickness out ofcopper tubing comprising the steps of, bending the copper tubing intothe shape of an elbow, locating the wall portions of said elbow whichare of reduced thickness due to such bending, immersing said Wallportions in an electrolytic solution, activating said solution to effectcopper electroplating on said elbow, and

withdrawing said wall portions from said solution at a rate inverselyproportional to the extent of reduction in wall thickness, whereby saidwall portions of greater reduction receive increased electroplating toprovide an elbow of uniform thickness.

7 ing reduced thickness due to such bending, immersing said wall portionin an electroyltic solution, activating said solution to efiectelectroplating of said wall portion, and graduaIIy'WithdraWing said wallportion from said solution so that the areas thereof are immersedtherein 7 for a period of time corresponding to the extent of reduction,whereby an elbow of uniform wall thickness is provided 6. A method offorming an elbow having uniform wall thickness out ofsubstantiallystraight copper tubing comprising the steps of, bending thecopper tubing into the shape of an .elbow, locating the wall portions ofsaid elbow which are of reduced thickness due to such bending; immersingsaid wall portions in an electrolytic solution, activating said solutionto efiectelectroplating of said wall portions, and controlling theimmersion time of said wall portions so that areas of greater reductionin wall. thickness spend a greater amount of time in said activatedsolution, to thereby 'provide an elbow having uniform Wall thickness.

References Cited in the file of this patent UNITED STATES PATENTS2,181,257 Arbogastt Nov. 28, 1939 2,229,077 Hammond et al. Ian. 21, 19412,358,104 Scavullo Sept. 12, 1944 2,780,019 Sullivan Feb. 5, 19572,879,209 Fialkolt Mar. 24, 1959

1. A METHOD OF FORMING AN ELBOW HAVING UNIFORM WALL THICKNESS OUT OFCOPPER TUBING COMPRISING THE STEPS OF, BENDING THE COPPER TUBING INTOTHE SHAPE OF AN ELBOW, LOCATING THE WALL PORTIONS OF SAID ELBOW WHICHARE OF REDUCED THICKNESS DUE TO SUCH BENDING, AND ELECTROPLATING ONOTSAID WALL PORTIONS SUFFICIENT COPPER TO OVERCOME SAID REDUCED THICKNESSTO THEREBY PROVIDE AN ELBOW OF UNIFORM WALL THICKNESS.